A high-resolution late Holocene speleothem record from Kaite Cave, northern Spain: δ18O variability and possible causes

Abstract

A high-resolution calcite oxygen stable isotopic (δ18O) record, covering the past 4000 years, was obtained from Kaite Cave, northern Spain. The record has a mean δ18O value of -6.25% VPDB and a range of 2%. Spectral analysis of the d18O data shows significant periodicities of 2400–1900, 600, 150, 27, and 22 years. The amplitudes during these periods range from 0.2% to 2%. Factors controlling the isotopic ratio in the speleothem were evaluated. The calcite is most likely precipitated under equilibrium conditions, with the cave calcite δ18O interpreted as a proxy of oxygen isotopic composition in local rainwater. Other factors such as temperature or fractionation in the karst system prior to calcite precipitation are considered of negligible or of minor importance. Mechanisms affecting rainfall isotopic composition were also investigated on different time scales. Precipitation amount is the primary factor controlling the high frequency d18O oscillations. Other climate parameters, such as changes of storm tracks may have significant contributions on centennial and millennial time scales.